JPH10319333A - Thermally compensated focusing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically correct a focus error caused by the change of a temperature condition in a plotting system by transmitting the detected temperature data of a medium supporting member to a control unit and adjusting the focus of a radiated beam on a medium. SOLUTION: The control unit 38 processes temperature data received from sensors 13, 19 and 57 in order to measure whether a movable lens is positioned so that the radiated beam 22 may be focused on the medium. The transmitted temperature data are processed by the control unit 38 in accordance with a thermal expansion coefficient and geometry to which the detected data are related. When the temperature of a cylindrical drum 14 rises, the drum 14 is expanded and material 12 is moved to be separated from a radiation source in a housing 18. Such an effect influences the focus of the beam 22 on material if focusing is not performed. In order to decide the direction and the amount of displacement necessary to adjust the focus, the control unit 38 previously calculates the adjusting amount and preserves it in a lookup table in the control unit 38 so that the lookup table preserved has only to be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to reading and recording images, and more particularly to adjusting the focus of an optical image beam to compensate for focus errors caused by environmental conditions within the imaging system.

[0002]

2. Description of the Related Art Recent image setters and plate setters write or record an image for the next reproduction or read a pre-recorded image at a predetermined resolution. Is using an optical scanner. Such scanners include light or heat sensitive paper or polymer films, light or heat sensitive coatings or erasable imaging materials, aluminum or other metal based printing plates or other types of media. It writes and records images on various media, or reads previously recorded images from them. The media is typically placed on a flat or curved image surface and then scanned with a light beam.

A key component of modern image and plate setting systems is an image processor that generates and / or edits digital images, and data signals from the image processor are used to generate light beams by the image setter or plate setter. A raster image processor (RIP) is included to convert the signal into a signal that can be understood by a controller that controls the scan.

The image setter or plate setter itself typically includes a scanning assembly that is often movably supported within a drum-type cylinder in which to record or be recorded. By means of the signals from the RIP and its own programmed instructions, the controller generates signals for controlling the optical scanning, which comprise one or more light beams while the cylinder itself remains stationary. This is for writing an image on the medium installed in the drum type cylinder or reading an image from the medium by scanning the inner circumference of the mold cylinder.

[0005] A typical scanning assembly for a cylindrical drum imaging system is a radiation source, such as a laser diode or other optical beam generator, on the inner periphery of the drum cylinder, as will be appreciated by those skilled in the art. One or more lenses for accurately focusing the light beam onto the image plane via a spin mirror or other optical device that scans the light beam.

[0006] The high resolution image setter and plate setter provide banding and dot gain / disappearance.
/ loss), an objectionable artifact (art
Precise focusing is required to obtain an output image without ifacts. Banding and / or dot gain may result from small variations in the beam spot size on the material or image receiving surface. Even though small deviations in the system focus do not significantly affect the beam spot size on the image receiving surface, spot size variations caused by dynamic variations in the focus are visible in the output image. Generates artifacts. When the system focus error is eliminated, the effect of dynamic focus fluctuations is minimized, thus reducing the source of banding.

[0007] Large format drawing devices have difficulty maintaining focus due to temperature changes in the optical system components and the support member on which the medium to be drawn is placed. In conventional writing systems, the focus is set at the factory, during initial installation, or during early use. Preferably, the focus is established based on the normal operating temperature of the writing system; however, the actual operating conditions generally characterize normal operating conditions due to the general environmental conditions in which the writing system operates. It may be different from the condition that may be attached. Further, the normal operating conditions typically change over time in the rendering system. Still further, some parts of the scanning assembly may be replaced during the life of the imaging system, and the new part may react differently from the replaced part under normal operating conditions. Absent. In addition, the drawing system may sometimes be activated shortly after startup, so that drawing may occur before the system reaches normal operating conditions. Either of these conditions can be a system focus error that significantly degrades the quality of the writing.

Recently, mechanisms have been developed that allow for dynamic adjustment of system focus within the image setting and plate setting systems. For example, U.S. Ser. No. 08 / 373,712, commonly assigned to the assignee of the present application, discloses a focusing mechanism that allows real-time focusing in an optical imaging system. As described therein, the adjustment mechanism allows precise focusing for various thicknesses of the writing material. However, there remains a need for a writing system in which the focus of the light beam is adjusted to correct for focus errors caused by variations in the operating conditions of the system.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a drawing system in which focus errors caused by changes in temperature conditions in the drawing system are automatically corrected.

It is another object of the present invention to provide a drawing system that maintains a desired focus regardless of the ambient conditions in which the drawing system operates.

It is a further object of the present invention to provide a drawing system wherein the focus of the system is adjusted in real time so that high quality drawing can be properly performed before the system reaches its normal operating conditions. That is.

Yet another object of the present invention is to provide a rendering system in which the focus is automatically adjusted to account for changes caused over time by use even under normal operating conditions. is there.

[0013] Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the present disclosure, including the following detailed description, as well as by practice of the present invention. While the invention will be described below with reference to preferred embodiments, it should be understood that the invention is not limited thereto. Here, those of ordinary skill in the art having access to the present disclosure will be aware of additional implementations, modifications and embodiments, as well as uses in other fields, which are disclosed and claimed in the scope of the invention. , Which make significant use of the present invention.

[0014]

SUMMARY OF THE INVENTION In accordance with the present invention, a writing system includes a radiating portion, such as a laser diode or a gas laser or an optical fiber termination, for emitting a beam of radiation along a beam path. An optical assembly, such as a lens, lens assembly or other optical element arrangement, focuses the emitted beam on the medium to be imaged. The system also includes a focusing mechanism, which may be, for example, part of the optical assembly. A medium support member, such as a cylindrical inner drum support, a rotating drum or a flat plate support, has a support surface for supporting the medium during drawing.
A sensor is provided for generating temperature data representing the detected temperature of the medium support member. The temperature data is transmitted to a controller, which controls the focus adjustment mechanism with the temperature data to adjust the focus of the emitted beam onto the medium.

[0015] The support surface is disposed along the beam path and is initially at an initial distance from the radiator. This distance is
For example, it may be a preset distance at the factory or at installation, or may involve a particular positioning of the support surface and the radiator at some point during system operation. At the detected temperature of the media support member, the support surface will be at a different distance from the radiator due to the thermal properties of the media support member. This means that due to a change in the temperature of the medium support member, the support member expands or contracts based on its coefficient of thermal expansion. Thus, the distance from the support surface to the radiator along the beam path changes, which change is a focus error in the medium to be imaged. Thus, the amount and direction of the focus adjustment corresponds to the difference between the initial and current distance.

According to another aspect of the invention, an optical system support member, which may be part of a traveling structure in an internal drum type image setter or plate setter, is spaced apart from the radiating and media support members. Supporting the optical assembly as described. A second sensor is provided for generating temperature data representing the detected temperature of the optical system support member. The controller utilizes this data with the temperature data from the media support member sensor to control the focusing mechanism with the received temperature data to adjust the focus of the emitted beam on the medium. Because of the thermal properties of both the optics support and the media support, the support surface of the media support is initially at some distance from the optical assembly, but the optics support and the media support At a different distance from the optical assembly at the detected temperature. Thus, in this case, the amount and direction of the focus adjustment correspond to the difference in the distance.

According to yet another aspect of the invention, the radiating portion has a housing, which may also act as a heat sink for the radiation source. Another temperature sensor is provided on the housing to further generate temperature data representing the detected temperature of the housing. This temperature data is transmitted to the controller. In this case, in order to properly adjust the focus of the emitted beam on the medium, the controller controls the focusing by means of temperature data associated with the medium support, the optics support and the radiator housing. It can be further adapted to control the mechanism.

If the temperature of the support member and the housing changes, the thermal properties of the respective elements may cause the media assembly to radiate between the media assembly and the radiator to the support. It will be appreciated by those skilled in the art that the distance of If the focus is set based on the actual or assumed temperature of each element different from the sensed temperature, the amount and direction of the focus adjustment will be between the radiator and the media support surface resulting from a change in temperature. And the change in distance between the radiating or supporting surface and the optical assembly. Changes in these differences can be easily calculated in a known manner using the respective coefficients of thermal expansion of each applied element. Of course, only those that undergo temperature changes in the support member and the housing need to be considered in the adjustment calculation. Rather than performing adjustment calculations in real time, a pre-built look-up table with pre-calculated adjustment data for various combinations of temperature data determines the required adjustment direction and amount. Can be used for

In its simplest form, radiation emitted along the beam path by a beam emitter initially located at a certain distance from a medium support member, which is at or assumed to be at an initial temperature. Beam focus is adjusted by detecting the actual temperature of the media support member and by adjusting the beam focus of the emitted beam according to the detected temperature of the media support member. If the radiation beam is
If the focussing device is at an initial temperature or passes through a focusing device supported by a focusing device support member assumed to be, the focusing device is drawn at a distance from the radiating portion and the radiating portion. Media. The actual temperature of the support member is detected and the beam focus is also adjusted by the detected temperature of the focusing device support member. This may include, for example, controlling the operation of the focusing device itself. Still further, if the radiator has a housing, an initial distance from the radiator to the medium support member is also set based on assuming that the housing is at or at an initial temperature. I have. It is also possible to detect the actual temperature of the radiator housing and to adjust the beam focus according to the detected temperature of the housing.

The technique described above is easily executed by a computer program stored in a storage medium such as a read only memory (ROM). The stored computer program is operative to receive a signal from the one or more temperature sensors and processes the received signal to generate a correction signal for adjusting the beam focus in response to the detected temperature. The focusing device can be read by the computer from the computer readable storage medium to cause the computer to transmit the correction signal to adjust the beam focus to cause the computer to transmit the correction signal.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS.
0, an imaging system comprising a photosensitive or radiation-sensitive recording material 12 on a support surface of a cylindrical drum-shaped platen 14, typical of known image setting devices, and a control system 30 is shown. . The scanning assembly 10 includes a radiation source, such as a light source or a laser, in a metal housing 18 mounted at a fixed distance from the support surface of the cylindrical drum 14. A lens assembly 20 is located between the light source in the housing 18 and the support surface of the drum 14 for focusing a beam 22 emitted by the light source located in the housing 18 onto the material 12. . Although shown as a spin mirror, a beam deflecting device 24, which may be of another type, linearizes the beam 22 across the material 12 supported on the support surface of the cylindrical drum 14. Scan.

The vehicle 11 is synchronized by an electronic control signal from the control system 30 to linearly scan the beam 22 over the material 12 on the support surface of the drum 14 to form the image. This allows for relative movement between the scanning assembly 10 and the material 12. In a capstan type imaging system, the vehicle typically includes rollers that move the material relative to the support surface during scanning. In the illustrated drum type imaging system, the traveling body 1
1 is the axis C of the drum 14 by a precise linear drive mechanism.
-C, while the material 12 remains stationary.

The photosensitive material is used to achieve input and read scanning in a similar manner by collecting and detecting light reflected or propagated through the previously drawn material in a similar manner. It will be appreciated by those skilled in the art that it can be replaced with the material drawn in the above. It will also be understood that the following description of the invention is equally applicable to reading previously exposed images from recorded material.

[0024] Other optical elements, such as mirrors, holographic, diffractive, binary, and / or graded index, may be used to focus the laser beam onto the material. Those skilled in the art will recognize that they can be included as part of the assembly 20. Further, the lens assembly 20 may be disposed before or after the beam deflecting device 24.

Referring to FIG. 1, the control system 30 includes a control panel 32 having a keypad 34 and a display 36 disposed therein. The control system 30 also receives image signals from a raster image processor and
2 includes a controller 38 that issues a signal to the scanning assembly 10 to drive the scanning of the beam 22 to form an image on the second. The controller 38 receives signals from temperature sensors located within the imaging system and controls signals to a dynamic focusing assembly included as part of the lens assembly 20, as described in more detail below. These signals are processed to generate As shown in FIG.
Is installed on the drum 14, and the controller 3 is connected by a communication line.
8 is connected.

As shown in FIG. 3A, the lens assembly 20
Is disposed between the light source in the housing 18 and the support drum 14. The assembly 20 has an elaborate focusing mechanism that focuses the beam 22 on an image receiving surface or photosensitive layer of the material 12 by precisely adjusting the focal point 48 of the light source within the housing 18. I have. Fine focusing is effective in reducing sources of banding artfact in the final output image. The lens assembly 20 has a fixed lens 44 in the beam path for focusing the beam 22.
That is, the lens 44 is positionally fixed to the light source and the support drum 14 installed in the housing 18. The movable lens 46 in the beam path is the fixed lens 4
4 is adjustable longitudinally along the optical axis BB. The movable lens 46 is a lens having a longer focal length than the fixed lens 44. The weak lens 46 may be a convergent lens or a divergent lens and may be located before, after, or inside the fixed lens in the beam path. Either or both of these lenses can be made as a lens group or a plurality of same groups using several lens elements.

Due to the relatively long focal length of the movable lens 46, the relatively large displacement of the lens 46 along the optical axis B--B will also result in a combination of the fixed and movable lenses, and thus This results in a relatively small change in the focal point 48 of the entire lens assembly 20. Accordingly, longitudinal displacement of the weak lens 46 along the beam path will result in a relatively small longitudinal displacement of the beam focus on the laser source image or the drawing surface.

As shown in the exploded view of the beam position in FIG. 3B, the displacement of the focal point 48 as indicated by arrow F due to the adjustment of the position of the weak lens 46 is much smaller than the displacement D of the lens 46. Therefore, in order to displace the second lens 46 in the lens assembly 20, an inexpensive and simple fine adjustment mechanism 50 can be used. Because of the long focal length of the weak lens 46, any lateral displacement of the weak lens 46 in a direction generally perpendicular to the optical axis BB has a negligible effect on the performance and alignment of the optical system. Thus, the positioning of the weak lens requires only a low-precision drive mechanism 50, while the lateral position of the beam focal point 48 on the drawing surface is kept narrowly constrained.

As a benefit, both the weak lens 46 and the adjustment mechanism 50 are inexpensive, allowing for easy and low cost focus adjustment. If the weak lens is placed in a divergent or convergent beam, the weak lens is not located at any longitudinal position along the optical axis so that it does not affect the focal point of the lens assembly. It will be appreciated by those skilled in the art that the design of weak lenses can be limited.

The precision focusing mechanism is easily controlled by the controller 38. The controller 38 controls the position of the focusing lens 46 by determining the required position of the focusing lens based on the detected temperature data, as described in more detail below. FIG. 3 shows that the light source housing 18 has a temperature sensor 19 attached thereto. The sensor 19 is connected to the controller 38 by a communication line as shown in FIGS. The controller 38 sends a signal to the adjustment mechanism 50 to adjust the focusing lens position longitudinally along the beam axis.

Referring to FIG. 4, a preferred embodiment of the adjusting mechanism of the lens assembly 20 will be described. The weak lens 46 is mounted in a lens holder 52, which is supported by two parallel leaf springs 54, one on each side of the lens holder 52. The leaf spring 54 is attached to the plate 56 forming part of the running body 11 and the lens holder 52 by screws 58 or other suitable means. The lens holder 52 has a through hole 6.
2 has a rigid screw 64 fixed in the rotation direction. When the nut 60 is rotated by the mini motor 66, the rotating nut 60 is engaged with the screw 64 to displace the lens mount 52 in the longitudinal direction. The screw 64 can be driven forward or reverse or linearly to displace the weak lens 46 toward or away from the first lens 44. The nut 60 is slightly oversized to allow bending of the screw 64 during movement of the mount 52.

A rectangular projection 68 in the longitudinal direction on the lens holder 52 is combined with a rectangular groove 70 in the longitudinal direction of the plate 56 to guide the lens mount 52 in the longitudinal direction when the lens mount 52 moves. The lens is maintained substantially perpendicular to the beam axis BB. As the lens mount 52 undergoes longitudinal movement, the leaf spring 54 flexes, causing some transverse or lateral displacement of the weak lens 46 with respect to the beam axis BB. Because of the long focal length of the weak lens 46, any transverse displacement of the weak lens 46 has negligible effect on the optical system.

Referring now to FIG. 5, another embodiment of the adjustment mechanism for the lens assembly 20 will be described. The weak lens 4
6 is a lens holder 52 supported by two parallel leaf springs 54, one on each side of the lens holder 52.
It is installed in. The leaf spring 54 is attached to the plate 56 forming part of the running body 11 and the lens holder 52 by screws 58 or other suitable means. The lens holder 52 has a nut 60 ′ whose rotation is fixed in the through hole 62. Flexible screw 64 '
Engages with the nut 60 'to displace the lens mount 52 longitudinally when the screw 64' is rotated by the minimotor 66. The screw 64 ′ is driven forward or backward, displacing the weak lens 46 closer to or away from the first lens 44.

A longitudinal rectangular protrusion 68 on the lens holder is combined with a longitudinal rectangular groove 70 in the plate 56 to guide the lens mount 52 longitudinally during movement of the lens mount 52. , The lens 4
6 is maintained substantially perpendicular to the beam axis BB. As the lens mount 52 undergoes longitudinal movement, the leaf spring 54 bends causing some transverse or lateral displacement of the weak lens 46 with respect to the beam axis BB. Because of the long focal length of the weak lens 46, any transverse displacement of the weak lens 46 has negligible effect on the optical system.

If the adjustable optical element combination has a relatively long combined focal length than the fixed optical element combined focal length, a mirror, holographic,
Other optical elements, such as diffractive, binary, graded index, etc., can be replaced or combined with a fixed lens for focusing the beam onto the material, and other optical elements Can be replaced or combined with an adjustable movable lens for the fixed element, as will be understood by those skilled in the art. Further, if necessary, the lens assembly 20 can be located downstream of the beam deflecting device 24. Elements performing the function of a lens for electromagnetic or particle beam radiation are within the scope of the invention. It will be appreciated that it is within the spirit of the present invention that various mechanisms can be used to displace the weak lens relative to the fixed lens. Control switch 67
Is provided on the motor 66 and is connected to the controller 38 for receiving a control signal from the controller 38 for controlling the operation of the motor 66.
To drive the required displacement of the weak lens 46 in a required direction. A thermal sensor 57 connected to the controller 38 is located on the vehicle plate 56 such that a signal representing the detected temperature of the support plate 56 is transmitted to the controller 38 for processing. You should be careful.

The operation of the image system shown in FIGS. 1 to 5 will now be described with reference to FIG. FIG. 6 shows FIG.
Scanning unit assembly 10 and control system 30 shown in FIGS.
3 is a block diagram of the various components of FIG. The operation of the scanner assembly is triggered by an operator entering a predefined command into the keypad 34, the command being transmitted by the communication link 130.
To the controller 38 via In response to the received signal, the controller 38 starts applying power to the drawing system. This also supplies power to the temperature sensors 13, 19, 57, so that each sensor immediately
The transmission of the temperature data to the controller 38 via 0 is started. The signal transmitted on link 150 is representative of the detected temperature of cylindrical drum 14, source housing 18, and vehicle support plate 58. As explained further below,
The controller 38 controls the weak lens 46 so that the focal point 48 of the radiation beam 22 is properly focused on the medium.
The sensor 13 to determine if
Process the temperature data received from 19 and 57.

In particular, the temperature data transmitted to the controller 38 is processed by the controller 38 according to the known coefficient of thermal expansion and geometry of the structural element to which the sensed data relates. For example, in the case of the cylindrical drum support 14, as the temperature of the cylindrical drum 14 increases, the drum expands, moving the material 12 away from the radiation source located within the housing 18. This affects the focal point of the beam 22 on the material if the weak lens 46 is not displaced to adjust the focal point 48. Similarly, as the temperature of the source housing 18 increases, the point of the source is displaced along the beam path toward or away from the material 12. This results in a misplacement of the focal point 48 in the material 12.

The distance between the radiation source installed in the housing 18 and the lens assembly 20 and the distance between the lens assembly 20 and the material 12 are determined by the thermal expansion of the traveling body installation plate 56. , The sensor 57
The temperature data transmitted from the controller 38 to the controller 38 determines the amount and direction of adjustment needed to offset any focusing errors caused by the relative displacement of the lens assembly 20 with respect to the source and the material being scanned. Can be processed for

In addition, the relative displacement between the weak lens 46 and the fixed lens 44 changes due to the thermal expansion of the support plate 56. Thus, the processor also uses the temperature data received from the sensor 57 to calculate the amount of adjustment of the weak lens required to offset the relative displacement between the lenses 44 and 46 due to thermal expansion of the plate 56. .

The calculation of the respective changes in the relative position of the various optical components along the radiation beam path due to the combined effects of the respective support and housing element temperature changes is performed in a conventional manner, and It involves merely routine calculations using known technical formulas. It is well understood by those skilled in the art that this calculation determines the total required adjustment of the weak lens 46. After determining the amount and direction of the required adjustment, the controller 38 generates a signal reflecting the temperature dependent data and transmits it to the motor 66 via the motor switch control 67 via the communication link 170. . In response to this signal, the motor drives the nut 60 or the screw 64 'to displace the weak lens 46 in the required amount and direction to place the focal point 48 on the material 12 at the desired position. I do.

As presented, the system operates on a real-time basis, so the weak lens automatically adjusts to compensate for temperature changes in the source housing 18, cylindrical drum support 14, and vehicle plate 56. Is adjusted to If necessary, a threshold value in the controller such that the adjustment is performed only if the thermal conditions of the housing 18, support 14, and vehicle 56 result in a displacement of the focal point 48 that is greater than an acceptable amount. Can also be saved. As described above, when each combination of temperature data is received, the controller determines the direction and amount of displacement needed to properly adjust the focal point 48 by using the stored look-up. The adjustments can be pre-calculated and stored in a look-up table in the controller 38 so that only a table is used. Alternatively, those skilled in the art will appreciate that the controller may use a simple algorithm to determine the direction of weak lens adjustment and the amount of displacement required for proper positioning of the focal point 48. It is possible.

It should also be appreciated that additional temperature sensors can be added if the imaging system includes additional optics and may be necessary. Furthermore, additional sensors can be used at many locations on each of the relevant temperature-sensitive elements in the system to provide even more accurate temperature information. For example, the motor 66
A sensor may be placed between the weak lens 46 and the weak lens 46 and between the weak lens 46 and the fixed lens 44. Additionally, a number of temperature sensors may be placed on the housing 18 and the drum support 14 and the temperature data may be used to calculate or otherwise determine the required displacement of the weak lens to properly position the focal point 48. Can be averaged to provide more accurate temperature data for use in It will further be appreciated that one or more sensors may be eliminated if desired, but with less accurate focusing.

The sensed temperature data used to determine any focus errors and make the necessary lens assembly adjustments is received by the controller just prior to drawing to ensure proper focusing of the imaging system. It is preferable that the data is obtained. If desired, the temperature data can be polled before drawing of each sheet of material or in some clocked order.

FIG. 7 is a somewhat simplified view of the control system 30. As shown in FIG. 7, the controller 38 includes a digital Purosesa 510, The processor may be a Pentium ^TM (Pentium ^TM) Purosesa example. Any commercially available keypad 34 or other input device can be used. The display 36 is a commercially available monitor. Preferably, the control system 30 is assembled from commercially available hardware components. The uniqueness of the controller 38 lies in the software instructions stored in its read only memory (ROM) 550.

In addition to the processor 510 and the read-only memory 550, the controller 38 controls the temperature sensor 13,
19 and 57 and a communication interface 570 for communicating with the motor 66. Those skilled in the art will recognize that the communication interface 570 also connects in a conventional manner with other imaging system components for conventional purposes. The communication with the motor 66 is
Includes those communications necessary to orient the movement of the weak lens 46 to adjust the position of the focus 48 due to focus errors caused by thermal conditions in the imaging system.

The input interface 520 provides an interface to the keypad 34, and the display interface 530 provides an interface to the display 36. The random access memory (RAM) 560 stores the processor 5 during system operation.
Provision is made for temporarily storing the data used by 10 and the programmed instructions of the controller. Bus 540 carries signals between the various components within controller 38 in a dedicated manner. The development of program instructions stored in the read-only memory 550 to instruct the processor 510 to operate as described herein is a matter that can be handled by routine programming.
It will be appreciated that it is easily accomplished by one of ordinary skill in the art without undue effort. Because the controller 38 is configured in a dedicated manner using conventional components, the general operation of the controller 38 is to a degree related to the particular programmed operation of the controller 38 according to the present invention. Will not be explained.

To initiate the operation, the operator inputs a programmed command from the keypad 34 or other operator input device. The input command is received by the input interface 520 and transferred to the processor 510 via the bus 540. The processor 510 is a read-only memory 550
Command the transfer of the appropriate program from the read only memory 550 to the random access memory 560 via the bus 540 for use during the operation in accordance with the programmed instructions stored in the memory. According to the stored programmed instructions, the processor 510 connects the bus 54 to the communication interface 570.
A signal is generated via the communication interface 570 to power the imaging system.

Applying power to the system generally includes applying power to the temperature sensors 13, 19, and 57 and the motor switch controller 67. If desired,
The processor 510, by means of the stored programmed instructions, instructs the motor 66 to make an initial adjustment in the positioning of the weak lens 46:
A further signal may be generated to the motor control switch 67 via the communication interface 570. Alternatively, at the end of each activation period, the processor 510, via its programmed instructions, via the communication interface to command the motor 66 to locate the weak lens at a predefined parking position. A signal transmitted to the motor switch 67 may be generated. In addition,
Still alternatively, the current position of the weak lens at the end of each operating period is stored in the random access memory 560 so that the next time the system operates, the sensor 1
The temperature data received from 3, 19 and 57 may be used in the process of determining the amount of displacement required for proper positioning of the focal point 48.

In any case, once the imaging system is in operation, the sensors 13, 19, and 57 transmit temperature data representing the detected temperatures of the respective components on which the sensors are located to the communication interface. 570 and bus 5
The data is transmitted to the processor 510 via the PC 40. The processor 510 determines the amount and direction of any adjustments required to position the weak lens 46 to properly position the focal point 48 on the material 12 according to its stored and programmed instructions, as described above. calculate. As described above, the processor 510 may make this determination or calculation on a continuous basis, or even during a specific time interval, or based on timing associated with the operation of the imaging system, for example, for each new sheet of material. May be performed immediately before drawing on the image.

The processor routinely monitors the received temperature data and automatically generates a signal to
6 and adjust the position of the weak lens to properly position the focal point 48 on the material based on the received temperature data from the sensor. Thus, the system operates as a closed loop focus correction system for automatically correcting the focus of the radiation beam on the material 12 in real time.

As described in detail above, the present invention provides an imaging system in which focusing errors caused by temperature conditions in the imaging system are automatically corrected. The described imaging system maintains the desired focus regardless of the ambient conditions in which the system operates. The imaging system of the present invention is configured to change the beam focus in real time so that high quality rendering is properly performed before the system reaches its normal operating conditions. Further, in the described imaging system, the focus is automatically adjusted to compensate for changes in the normal operating conditions of the system due to use and life.

Also, while the present invention has been described above using one or more preferred embodiments, those skilled in the art will recognize that the present invention is not limited thereto. The various features and aspects of the invention described above can be used individually or in combination. Further, while the invention has been described in context of being implemented for a particular purpose in a particular environment, its usefulness is not limited thereto, and the invention may be advantageously used in any number of environments and implementations. What is possible is recognized by those skilled in the art. Therefore, the following claims should be considered in light of the full spirit and spirit of the invention disclosed herein.

Preferred embodiments of the present invention are as follows.

1. In an imaging system with a beam focus adjustment function, a radiation beam (2
An optical assembly (2) having a radiator configured to emit 2) and a focusing mechanism configured to focus the emitted beam on a medium (12) to be imaged.
0), a medium support member (14) having a support surface configured to support the medium during the writing, and a sensor configured to generate first temperature data representing a detected temperature of the medium support member. (13) and comprising a controller (38) configured to control the focusing mechanism with the first temperature data to adjust the focus of the emitted beam onto the medium. Characteristic imaging system.

2. The imaging system of claim 1, wherein the support surface is firstly disposed along a beam path at a first distance from the radiator, and the support surface is provided at the detected temperature of the medium support member. Is located at a second distance from the radiating portion different from the first distance due to thermal properties of the medium support member, and wherein the amount and direction of the focus adjustment is a first and a second. 2. An imaging system characterized in that it corresponds to the difference between the distances. 2. The imaging system according to claim 2, wherein the thermal characteristic is a coefficient of thermal expansion.

4. The imaging system of claim 1, further comprising an optical system support member (5) configured to support the optical assembly so as to be spaced apart from the radiating portion and the medium support member.
6) and a second indicating the detected temperature of the optical system support member.
A second sensor (57) configured to generate the first and second temperature data, wherein the controller adjusts the focus of the emitted beam onto the medium. An imaging system, further configured to control the focusing mechanism with data.

5. In the imaging system of claim 4, the support surface is initially located along the beam path at a first distance from the optical assembly, and at a detected temperature of the optical system support member, and At the sensed temperature of the media support member, the support surface is different from the first distance from the optical assembly due to the thermal characteristics of the optics support member and the thermal characteristics of the media support member. An imaging system, wherein the imaging system is spaced apart by a distance and the amount and direction of the focus adjustment corresponds to a difference between the first and second distances.

6. 2. The imaging system according to claim 2, wherein the thermal characteristic is a coefficient of thermal expansion.

7. The imaging system of claim 1, further comprising an optical system support member (5) configured to support the optical assembly so as to be spaced from the radiating portion and the medium support member.
6), a radiator housing (18) configured to receive the radiator, and a second sensor (57) configured to generate second temperature data representing a detected temperature of the optical system support member. ) And a third sensor configured to generate third temperature data representative of a detected temperature of the radiator housing, wherein the controller focuses the emitted beam on the medium. An imaging system, further configured to control the focus adjustment mechanism with first, second, and third temperature data for adjustment.

8. In the imaging system of claim 7, the support surface is initially disposed along the beam path at a first distance from the optical assembly, and the optical assembly is firstly disposed from the radiating section to a second one. At a distance along the beam path, at the detected temperature of the optical system support member, and at the detected temperature of the medium support member, the support surface is adapted to the thermal characteristics of the optical system support member and the thermal characteristics of the optical system support member. A third distance that is different from the first distance due to thermal properties of the media support member and is located away from the optical assembly, at a sensed temperature of the optical system support member, and At the detected temperature, the fourth distance between the radiator and the optical assembly may be different from the second distance due to the thermal characteristics of the optics support member and the radiator housing. And the amount and direction of the focus adjustment are the difference between the first and third distances and the second and fourth distances. Imaging system characterized in that it corresponds to the difference.

9. 2. The imaging system according to claim 2, wherein the thermal characteristic is a coefficient of thermal expansion.

10. The medium supporting member (1) at the first temperature
4) A method for adjusting the focus of a radiation beam (22) emitted along a beam path by a beam radiator located at a distance from 4), wherein said first temperature of said medium support member differs from said first temperature. Detecting a second temperature (13); and adjusting a beam focus of the emitted beam according to the detected second temperature of the medium support member. A method for adjusting the focus.

11. In the above method, the medium support member is initially positioned along the beam path at a first distance from the radiator, and at a detected second temperature of the medium support member, A radiator is located at a second distance different from the first distance from the media support member due to thermal characteristics of the media support member, and the amount and direction of adjustment of the beam focus is different from the first and second distances. A method for accommodating a second distance difference.

12. The method according to claim 11, wherein the thermal characteristic is a coefficient of thermal expansion.

13. A medium to be drawn with the radiating part (12)
The beam passes through a focusing device (20) supported by a support member (56) at a distance from the radiator where the support member is at a first temperature. The method includes detecting a second temperature of the support member different from the first temperature, and adjusting a beam focus of the emitted beam according to the detected second temperature of the support member. A method comprising:

14. The method of claim 13, wherein adjusting the focus includes controlling operation of the focusing device (38).

15. In the above thirteenth method, the focusing device is first positioned along the beam path at a first distance from the radiator and at the detected second temperature of the support member, A radiator is located at a second distance from the focusing device that is different from the first distance due to thermal properties of the support member, and the amount and direction of adjustment of the beam focus is first and second. A method corresponding to the difference between the two distances.

16. The method according to claim 11, wherein the thermal characteristic is a coefficient of thermal expansion.

17. The method of claim 10, wherein the beam radiator has a beam radiator housing at a first temperature, further comprising: detecting a second temperature different from the first temperature of the beam radiator housing; Adjusting the beam focus of the emitted beam according to a second temperature.

18. In the above method, the medium support member is first positioned along the beam path at a first distance from the radiator, and at the detected second temperature of the beam radiator housing. The radiator is located at a second distance different from the first distance from the media support member due to thermal properties of the beam radiator housing, and the amount and direction of adjustment of the beam focus The method corresponds to the difference between the first and second distances.

19. The method of claim 11, wherein said thermal characteristic is a coefficient of thermal expansion.

20. An article of manufacture for adjusting the focus of the radiation beam (22) emitted by the radiation generator along the beam path, said radiation beam being arranged on said beam path; And focused by a beam focusing device (20) positioned between the radiation generator and a media support member (14) for supporting a media (12) to be imaged, the media support member being mounted thereon. The first temperature sensor (1
3) and wherein the radiation generator is located at a first distance from the medium support member at a first temperature, the computer readable storage of the one product. A medium (550), and a computer program (programming) stored in the storage medium, wherein the stored computer program is readable by the computer from a storage medium readable by the computer, and , Thereby causing the computer to operate, wherein the operation is performed by the first temperature sensor from the first temperature sensor representing a second temperature different from the first temperature of the medium support member. Receiving the signal and processing the first signal to generate a correction signal that adjusts the beam focus to correspond to a second temperature of the medium support member (510); and the focusing device. Is the beam An article of manufacture, characterized by transmitting the correction signal operative in response to adjust focus.

21. In one product of the above 20,
The radiation generator includes a housing (18) having a second temperature sensor (19) mounted thereon, the radiation generator being at a first distance from the medium support member at the first temperature. Located, the generator housing is at a third temperature, and the stored computer program is readable by the computer from the computer readable storage medium to cause the computer to operate therewith. And configured to receive a second signal from the second temperature sensor representative of a fourth temperature different from the third temperature of the generator housing to generate a correction signal. The modified signal is generated to further adjust the beam focus to correspond to a fourth temperature of the generator housing, such as to process (510) the second signal. One of the product, characterized in that.

22. In one product of 21 above,
The focusing device is supported by a focusing device support member (56) having a third temperature sensor (57) mounted thereon, the focusing device relocating the generator housing at the third temperature. Radiation generator having a second
And the focusing device support member is at a fourth temperature, and the stored computer program causes the computer to read from the computer readable storage medium to cause the computer to operate therewith. The operation is for receiving a third signal from the third temperature sensor representing a sixth temperature different from the fifth temperature of the focusing device support member. And for processing the third signal to generate a correction signal, the correction signal further adjusting the beam focus to correspond to the sixth temperature of the focusing device support member. An article of manufacture characterized by being generated as described above.

[Brief description of the drawings]

FIG. 1 is a side view of a scanner assembly of a cylindrical drum imaging system of the present invention.

FIG. 2 is a sectional view of the scanning unit assembly of FIG. 1;

FIG. 3 is a more detailed view of the optical system portion of the scanning assembly shown in FIG.

FIG. 4 is a perspective view showing further details of a preferred embodiment of the lens adjusting mechanism shown in FIG. 3;

FIG. 5 is a perspective view showing further details of a preferred embodiment of the lens adjusting mechanism shown in FIG. 3;

FIG. 6 is a block diagram illustrating the flow of selected input and output signals of the controller of FIG. 1 according to the present invention.

FIG. 7 is a simplified block diagram of the controller of FIG. 1 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Scanning assembly 11 Running body 12 Radiation-sensitive recording material 13, 19, 57 Sensor 14 Drum type impression cylinder 18 Housing 20 Lens assembly 22 Beam 24 Beam deflector 30 Controller 32 Control panel 34 Keypad 36 Display 38 Control Instrument 44 Fixed lens 46 Movable lens 48 Focus 50 Fine adjustment mechanism 52 Lens holder 54 Leaf spring 56 Plate 58 Screw 60 Rotating nut 60 'Fixed nut 62 Through hole 64 Rigid screw 64' Flexible screw 66 Mini motor 67 Switch controller 68 Projection 70 Groove 130, 150, 170 Communication link 510 Digital processor 520 Input interface 530 Display interface 540 Bus 550 Read only memory 560 Random access memory 57 0 Communication interface

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Claims (3)

[Claims] 1. An imaging system having a beam focus adjustment function, comprising: a radiation section configured to emit a radiation beam along a beam path; and focusing the emitted beam on a medium to be imaged. An optical assembly having a focus adjustment mechanism configured to: a medium support member having a support surface configured to support the medium during the writing; and a first temperature representative of a detected temperature of the medium support member. A sensor configured to generate data, and a controller configured to control the focusing mechanism with the first temperature data to adjust the focus of the emitted beam onto the medium. An imaging system, comprising: 2. A method for adjusting the focus of a radiation beam emitted along a beam path by a beam emitter located at a distance from a medium support member at a first temperature. Detecting a second temperature of the member different from the first temperature; and adjusting a beam focus of the emitted beam according to the detected second temperature of the medium support member. A method for adjusting focus. 3. An article of manufacture for adjusting the focus of a radiation beam emitted by a radiation generator along a beam path, said radiation beam being arranged on said beam path and said radiation Focused by a beam focusing device positioned between the generator and a media support member for supporting the medium to be imaged, the media support member having a first temperature sensor mounted thereon; And the radiation generator is adapted to generate a first radiation from the medium support member at a first temperature.
In the one product, which is positioned at a distance of: a storage medium readable by a computer, and a computer program stored in the storage medium, wherein the stored computer program is It is configured to be readable by a computer from a computer readable storage medium, and thereby to cause the computer to operate, wherein the operation is performed by comparing the first temperature of the medium support member with the first temperature. Receiving a first signal from the first temperature sensor representative of a different second temperature and generating a correction signal for adjusting the beam focus to correspond to a second temperature of the medium support member; One article of manufacture wherein the first signal is processed and the focussing device transmits the correction signal operative in response to adjust the beam focus.